Moving DTensor to be in the public namespace, to formally add the
documentation page that includes all the public APIs. This includes:
* many path renames and path import fixes
* a dedicated doc page without too much content yet (adding in the next
PRs)
* To preserve the BC for users still using the `torch.distributed._tensor`,
I added a shim script to redirect old path calls to the new module
The BC preserving is evidented by the fact that all DTensor tests are still
working without changing the public imports. So it's safe to land the
changes
Pull Request resolved: https://github.com/pytorch/pytorch/pull/133113
Approved by: https://github.com/XilunWu
ghstack dependencies: #133305, #133306
**Summary**
This PR adds a new private placement type `_StridedShard` for FSDP2 + TP style tensor sharding. The previously used `Shard` placement type cannot produce correct `full_tensor()` result because it assumes the tensor to be first sharded over `dp` mesh dimension then `tp` mesh dimension which does not hold true in FSDP2 + TP case.
**Test**
`pytest test/distributed/_tensor/test_utils.py -s -k strided_sharding`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/126697
Approved by: https://github.com/wanchaol
Summary:
Same as D57688538, recreated because of GH issues
This diff introduces LocalShardsWrapper which is crucial to migrating from using ShardedTensor to DTensor in TRec state dict representation. As well as any changes needed in PT-D and ModelStore to support this.
It allows us to extend DTensor to support multiple shards on a rank as well as empty shards on a rank as needed by TRec sharding logic.
This diff also extends the support for LocalShardsWrapper to be used in conjunction with DTensor in checkpointing cases (ModelStore and DCP)
See D54375878 for how it is used.
**LocalShardsWrapper supports the following torch ops:**
+ torch.ops._c10d_functional.all_gather_into_tensor.default
+ aten._to_copy.default
+ aten.view.default
+ aten.equal.default
+ aten.detach.default
With extensibility to add more as required by use cases.
See https://docs.google.com/document/d/16Ptl50mGFJW2cljdF2HQ6FwsiA0scwbAbjx_4dhabJw/edit?usp=drivesdk for more info regarding design and approach.
NOTE: This version of LocalShardsWrapper does not support empty shards, that is added in the next diff enabling CW. D57063512
Test Plan:
` buck test mode/opt -c python.package_style=inplace aiplatform/modelstore/client/tests_gpu:dist_checkpoint_save_load_with_stateful_tests -- --print-passing-details`
`buck2 test 'fbcode//mode/dev-nosan' fbcode//torchrec/distributed/tests:test_tensor_configs -- --print-passing-details`
Sandcastle
Reviewed By: XilunWu, wanchaol
Differential Revision: D58570479
Pull Request resolved: https://github.com/pytorch/pytorch/pull/129150
Approved by: https://github.com/XilunWu
This PR changes the traced_tangents field of ViewAndMutationMeta to be cache safe. Specifically, at runtime, the only time we need the fw_metadata's traced_tangent's field is for Tensor subclass metadata from __tensor_flatten__. So instead of storing an entire FakeTensor, which has many fields that can be unserializable, only store the result of __tensor_flatten__() on any FakeTensors representing subclasses.
That said, there's no guarantee that `__tensor_flatten__` is actually serializable: if we fail to pickle the result of __tensor_flatten__ we won't save to the cache.
To do this, we also make a small change to `__coerce_same_metadata_as_tangent__`, so that it takes in the return value of tensor_flatten() instead of an entire FakeTensor. Let me know if we should change the name of the function.
By doing this, we can now run the dynamic shapes cache test with autograd turned on.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/127618
Approved by: https://github.com/bdhirsh
as titled, given that our DTensorSpec is immutable, we can always reuse
the spec if the input/output have the same tensor metadata. this helps two fold:
1. We don't need to re-calculate the hash everytime we produce a
DTensorSpec, reduce runtime operator overhead
2. reduce the DTensor construction overhead.
Some local benchmark on a 800 parameter clip_grad_norm shows that for
foreach_norm the CPU overhead reduces from 11ms -> 7.8ms (around 30% improvement)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/128112
Approved by: https://github.com/awgu
Use `typing_extensions.deprecated` for deprecation annotation if possible. Otherwise, add `category=FutureWarning` to `warnings.warn("message")` if the category is missing.
Note that only warnings that their messages contain `[Dd]eprecat(ed|ion)` are updated in this PR.
Resolves#126888
- #126888
This PR is split from PR #126898.
- #126898
------
Pull Request resolved: https://github.com/pytorch/pytorch/pull/127689
Approved by: https://github.com/Skylion007
Use `typing_extensions.deprecated` for deprecation annotation if possible. Otherwise, add `category=FutureWarning` to `warnings.warn("message")` if the category is missing.
Note that only warnings that their messages contain `[Dd]eprecat(ed|ion)` are updated in this PR.
UPDATE: Use `FutureWarning` instead of `DeprecationWarning`.
Resolves#126888
- #126888
Pull Request resolved: https://github.com/pytorch/pytorch/pull/126898
Approved by: https://github.com/albanD
Fixes https://github.com/pytorch/pytorch/issues/122459, https://github.com/pytorch/torchtrain/issues/61
Even with the previous PR ("support DTensor/subclass constructors directly in the graph"), I still see some errors when running the repro above that start some logs showing that dynamo is inlining `__new__`.
I noticed that putting `@torch._dynamo.disable` on DTensor's `__new__` makes the entire repro pass.
Why does having dynamo try to inline `Subclass.__new__` run into problems? Morally, dynamo probably shouldn't be inlining __new__ ("creating a subclass" is a blackbox operation that AOTAutograd can trace through anyway). But concretely, we can end up with a node in the dynamo FX graph that has a "partially initialized tensor subclass" as its example value, because the subclass has been created but its fields have not been assigned to yet.
This breaks a bunch of invariants throughout dynamo: there are many places where if we have a tensor subclass node, we want to look at its inner tensors, to see if they are FakeTensors, what their FakeTensorMode is, and if they have dynamic shapes.
One option is to decide that "uninitialized subclass" is a first-class thing that anyone looking at the FX node examples values on the dynamo graph needs to handle, but this seems like a lot of work when in reality we don't need dynamo to trace the __new__ at all. Hence the `torch._dynamo.disable`.
I still wasn't very satisfied, since it was unclear to me **why** dynamo was inlining the `__new__` call, instead of interposing on the `DTensor()` constructor directly. After a long chat with @anijain2305, he explained that with code like this:
```
@torch._dynamo.disable(recursive=False)
def f(x):
out = SubclassConstructor(x)
```
Dynamo will never get the chance to interpose on the subclass constructor. Instead, what will happen is:
(1) Dynamo hands back control to cpython to run `f()`, since we disabled that frame
(2) `SubclassConstructor(x)` is run in eager mode
(3) `SubclassConstructor(x)` eventually calls `SubclassConstructor__new__`
(4) this is a new frame, that cpython then allows dynamo to intercept and start compiling
So it looks like we are basically forced to handle the situation where dynamo might directly start compiling `Subclass.__new__`
All of the above does not explain the story for `__torch_dispatch__` though. Empirically, I have a repro in torchtrain where looking at the dynamo logs, we see dynamo try to inline `__torch_dispatch__`.
```
[rank0]:DEBUG: Skipping frame because no content in function call _prepare_output_fn /data/users/hirsheybar/b/pytorch/torch/distributed/tensor/parallel/style.py 318
[rank0]:DEBUG: torchdynamo start compiling __torch_dispatch__ /data/users/hirsheybar/b/pytorch/torch/distributed/_tensor/api.py:297, stack (elided 5 frames):
```
I haven't been able to create a smaller repro of the problem (even using `_dynamo.disable(recursive=False)`), although in theory, if there is a `torch.*` op that you were to inline (where one of the inputs is a subclass), the next frame would likely be `__torch_dispatch__`. Dynamo always treats `torch.*` operations as not-inlinable though, so in theory we shouldn't ever see dynamo inline `__torch_dispatch__`, but a `_dynamo.disable()` fixes the problem.
I asked Animesh if we can have dynamo automatically apply this behavior to subclasses instead of needing it to be added explicitly. He pointed out that for `disable(recursive=False)`, we can't really do this within dynamo
Pull Request resolved: https://github.com/pytorch/pytorch/pull/123347
Approved by: https://github.com/zou3519
ghstack dependencies: #122502, #122751, #123348
This PR refactors the schema_suggestions in OuputSharding to be a single
OpSchema instead of list of schemas, which in practice we only have one,
for the multiple resharding case we also moved to OpStrategy so there's
no case that needs it to be a list
Pull Request resolved: https://github.com/pytorch/pytorch/pull/122929
Approved by: https://github.com/tianyu-l
This PR is enough to fix https://github.com/pytorch/pytorch/issues/118600.
More description of the problem is in the issue, but the high-level problem is similar to the "tangents might be non-contiguous" problem that we handle today, via forcing all tangents to be contiguous. There, the problem was something like:
"We guessed the tangent strides incorrectly, because strides on the runtime tangents were different from strides on the forward outputs, which we used to generate tangents"
Here, the problem is similar:
"We guessed the tangent tensor subclass's metadata incorrectly, because the runtime tangent was a subclass with different metadata than the forward output subclass".
This happened in an internal DTensor issue, where the metadata in question was the `placements` (shard vs. replicate vs. Partial).
One option is to solve this problem via backward guards. This is needed to unblock internal though, so I figured handling this similarly to how we handle non-contiguous tangents would be reasonable. I did this by:
(1) Assert that the metadata on subclass tangents is the same as what we guessed, and if not raise a loud error
(2) In the error message, provide the name of an optional method that the subclass must implement to handle this case:
`def __force_same_metadata__(self, metadata_tensor):`: If the forward output had a `Replicate()` placement, but the runtime tangent had a `Shard(1)` placement, this method allows a subclass to take the tangent and "convert" it to one with a `Replicate()` placement.
`__force_standard_metadata__(self)`: One issue is that there is another placement called `_Partial`, and its semantics are such that DTensor is **unable** to convert a DTensor with some placement type into another DTensor with a `_Partial` placement.
`__force_standard_metadata__` is now called on all (fake) subclass forward outs at trace-time to generate tangents, and gives subclasses a chance to "fix" any outputs with metadata that they cannot convert to later. Morally, this is similar to the fact that we force a `contiguous()` call on all tangents at trace-time.
I'm interested in thoughts/feedback! Two new dunder methods on traceable subclasses is definitely a contentious change.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/118670
Approved by: https://github.com/ezyang
This PR fixed the bug of redistribute to move early return check into the
redistribute autograd function, so that even though we redistribute the
same placement, the grad_placements from the `to_local` call might be
different, the redistribute backward still need to happen
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121653
Approved by: https://github.com/awgu
async output option was only available in `full_tensor()` call, but I think it's
generally good to make this option available in the `redistribute` call directly
so that user can control it
This PR adds async_op option to redistribute call, to allow user control
whether to perform tensor redistribution asynchronously or not.
By default we set this to False, this is to follow the semantics of the c10d
collectives.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121477
Approved by: https://github.com/wz337
This does not introduce a new test but is tested by checking that all the classes we already have still behave as before now that they don't explicitly disable torch_function.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120632
Approved by: https://github.com/ezyang
to_local accepts a `grad_placements` if user choose to pass, previously
we enforce the grad_out to be the "same" placement as the current
DTensor for safety.
But I realized that we DO NOT need to enforce this constraint. Why?
backward placement does not need to be the same as fwd tensor placement, this
is already the case for param vs param.grad (i.e. param can be replicate
and grad can be partial), so we should not restrict this to activation
vs activation grad too
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121474
Approved by: https://github.com/awgu, https://github.com/yoyoyocmu, https://github.com/yifuwang
This is a BC breaking change to distribute_module. The underlying rationle
for this change is that sometimes in the input_fn/output_fn, user would want
to access to the current module for some attributes. This might not be
common enough, but in some cases it's worth to access to the module.
An outstanding use case we want to support is float8, if we want to make
float8 works with the TP API, the input_fn/output_fn of TP parallel
styles would need to get access to the module, where the module might
encapsulates `dynamic_linear.emulate` attribute, that is useful for
input/output casting
Since this is needed for fp8 and DTensor still under prototype release,
I feel it's worth the change and it's better we make the change as
early.
Right now making it a soft BC breaking, which means we maintain BC still
but throw deprecation messages.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120895
Approved by: https://github.com/tianyu-l
The existing warning in `DTensor.__new__()` checks `if requires_grad != local_tensor.requires_grad:` and warns with:
> To construct DTensor from `torch.Tensor`, it's recommended to use `local_tensor.detach()` and make `requires_grad` consistent.
Calling `local_tensor.detach()` will have the returned `Tensor` have `requires_grad=False`, so the error message refers to the case where `local_tensor.requires_grad is True` but the user passed `requires_grad=False` to `to_local()`.
However, there is the converse case, where `local_tensor.requires_grad is False` but the user passed `requires_grad=True`. In this case, the original `if requires_grad != local_tensor.requires_grad:` check succeeds, and the warning is emitted. However, the warning message does not apply in that case.
This can happen via `_prepare_output_fn` -> `redistribute` -> `Redistribute.forward()`, where `output.requires_grad is False` but it passes `requires_grad=input.requires_grad` which can be `True`.
We should not warn in this case since `Redistribute.forward()` is our own framework code, so I was proposing to relax the warning.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/118186
Approved by: https://github.com/XilunWu, https://github.com/wanchaol
ghstack dependencies: #117994
This PR:
- refactors the redistribute implementation logic to make it more
sound, by figuring out the transform informations first and then apply
transformation step by step, we also cache the decisions so that it
could be reuse again
- for uneven sharding, refactor uneven sharding logic, and use a logical
shape concept for each transform information to fix the uneven sharding
multi-mesh redistribute bug
fixes https://github.com/pytorch/pytorch/issues/115310
Pull Request resolved: https://github.com/pytorch/pytorch/pull/115525
Approved by: https://github.com/XilunWu
Summary:
This change makes the `DTensor.from_local()` placements in backward pass from `Partial()` to `Replicate()` as pass through for following reasons:
1. When we run backward pass of DTensor.from_local, if the target placement is partial() (i.e. from user manual overwrite code instead of torch_dispatch) we keep the grad as replicate. This is because converting the gradients back to `Partial()` is meaningless.
2. The current div logic will lead to wrong numerical value in the above case.
Test Plan:
**CI**:
CI Tests
**Unit test**:
`buck2 test mode/dev-nosan //caffe2/test/distributed/_tensor:redistribute`
- Passed
**With model training**:
```
# We tested the case where input tensor is manually overwrite as Partial() and
# output tensor manually overwrite to Shard() then to local.
# Before the change: numerical value not correct
Forward pass:
collective: ReduceScatter
backward pass:
collective: AllGather + div by process group size
# After the change: div is removed as expected.
Forward pass:
collective: ReduceScatter
Backward pas:
collective: AllGather
```
Differential Revision: D52175709
Pull Request resolved: https://github.com/pytorch/pytorch/pull/115967
Approved by: https://github.com/wanchaol
Summary:
Rename _device_mesh.py to device_mesh.py, update all callsites, add documentation.
We created stubs for public class and methods in torch.distributed.device_mesh so that torch.distributed.device_mesh can be imported with or without distributed is available().
Original diff reverted: D51629761
Original PR reverted: https://github.com/pytorch/pytorch/pull/115099
Prior to landing, CI signals are all passed. Shipit added the "ci/trunk" label to the PR and DID NOT wait for it and went ahead committing. More context can be found in the reverted PR above.
Test Plan: CI.
Differential Revision: D51861018
Pull Request resolved: https://github.com/pytorch/pytorch/pull/115193
Approved by: https://github.com/fegin
Continuation of #112185, following the design in this [doc](https://docs.google.com/document/d/1ipSxcTzEMMOAPvxP-YJlD5JBZZmIGgh8Q34ixtOUCRo).
Summary:
* Introduce `SubclassSymbolicPolicy` containing separate dynamic dim / constraint policies for the outer and inner tensors
* Expand the automatic dynamic algorithm to recurse into inner tensors and produce one of these for a subclass instance
* Maintain legacy behavior for subclasses by recursively calling `mark_dynamic()` on inner tensors *of the same dim as outer* when `mark_dynamic(outer, ...)` is called
* Addresses this: 6a86cf00ad/torch/_dynamo/variables/builder.py (L1750)
* Add `outer_size` and `outer_stride` arguments to `__tensor_unflatten__()` so that you can find out what symbols were allocated for the outer size / stride (you are expected to return a tensor that compares equal to the outer symbols)
* Signatures now:
```python
# attrs is a list of inner tensor attributes on x; inner_tensor = getattr(x, attr)
# ctx is anything useful for rebuilding the class we want to guard on
attrs, ctx = x.__tensor_flatten__()
...
# inner_tensors is a dict of {attr -> tensor}
# ctx is taken unmodified from flattening and (eventually) guarded on
# outer_size is the expected size of the output; possibly symbolic
# outer_stride is the expected strides of the output; possibly symbolic
y = MySubclass.__tensor_unflatten__(inner_tensors, ctx, outer_size, outer_stride)
# at the __tensor_unflatten__() call-site in PT2, we assert y.shape == outer_size and y.stride() == outer_stride
# the assert simplifies symbols when there are relationships between outer and inner symbols
```
* Size info needed for `NestedTensor` at least, stride info needed for `DTensor` at least
* Punting on `outer_storage_offset` because storage_offset handling is horribly broken in PT2 right now
* ~~Add new `__tensor_mark_dynamic__()` to allow overriding the behavior of mark_dynamic on a per-subclass basis~~ (booted to future work)
* ~~Add guards for tensor subclasses by calling `__tensor_flatten__()` in the guard to test equality on `ctx`~~
* Now handled in #114469
* Next PR: add TENSOR_MATCH guards on inner tensors
Pull Request resolved: https://github.com/pytorch/pytorch/pull/114311
Approved by: https://github.com/ezyang, https://github.com/drisspg, https://github.com/voznesenskym, https://github.com/bdhirsh
Summary:
Rename _device_mesh.py to device_mesh.py, update all callsites, adds documentation.
Original diff reverted: D51629761
Original PR reverted: https://github.com/pytorch/pytorch/pull/114991
It was failing because failing a public module binding tests in MacOS, and this is due to the change in import order for torch/distributed/fsdp/_common_utils.py. Since this original import would still work, we remove the changes in this file.
Test Plan: CI.
Differential Revision: D51825114
Pull Request resolved: https://github.com/pytorch/pytorch/pull/115099
Approved by: https://github.com/wanchaol, https://github.com/fegin
